Pollen analysis, particle size analysis, end-member modelling and x-ray fluorescence measurements from sediment cores off Cape Ghir, Morocco@en

Understanding past human-climate-environment interactions is essential for assessing the vulnerability of landscapes and ecosystems to future climate change. This is particularly important in southern Morocco where the current vegetation is impacted by pastoralism, and the region is highly sensitive to climate variability. Here, we present a 2000-year record of vegetation, sedimentation rate, XRF chemical element intensities, and particle size from two decadal-resolved, marine sediment cores, raised from offshore Cape Ghir, southern Morocco. The results show that between 650 and 850 AD the sedimentation rate increased dramatically from 100 cm/1000 years to 300 cm/1000 years, and the Fe/Ca and pollen flux doubled, together indicating higher inputs of terrestrial sediment. Particle size measurements and end-member modelling suggest increased fluvial transport of the sediment. Beginning at 650 AD pollen levels from Cichorioideae species show a sharp rise from 10% to 20%. Pollen from Atemisia and Plantago, also increase from this time. Deciduous oak pollen percentages show a decline, whereas those of evergreen oak barely change. The abrupt increase in terrestrial/fluvial input from 650 to 850 AD occurs, within the age uncertainty, of the arrival of Islam (Islamisation) in Morocco at around 700 AD. Historical evidence suggests Islamisation led to population increase and development of southern Morocco, including expanded pastoralism, deforestation and agriculture. Livestock pressure may have changed the vegetation structure, accounting for the increase in pollen from Cichorioideae, Plantago, and Artemisia, which include many weedy species. Goats in particular may have played a dominant role as agents of erosion, and intense browsing may have led to the decline in deciduous oak; evergreen oak is more likely to survive as it re-sprouts more vigorously after browsing. From 850 AD to present sedimentation rates, Fe/Ca ratios and fluvial discharge remain stable, whereas pollen results suggest continued degradation. Pollen results from the past 150 years suggest expanded cultivation of olives and the native argan tree, and the introduction of Australian eucalyptus trees. The rapidly increasing population in southern Morocco is causing continued pressure to expand pastoralism and agriculture. […]理解过去的人类-气候-环境相互作用，对于评估景观与生态系统应对未来气候变化的脆弱性至关重要。这一点在摩洛哥南部尤为关键：当地当前植被受畜牧活动影响，且该区域对气候波动高度敏感。本研究基于取自摩洛哥南部吉尔角近海的2根十年分辨率海洋沉积物岩芯，构建了一套时长2000年的植被、沉积速率、X射线荧光（XRF）化学元素强度以及粒度记录。研究结果显示，公元650年至850年间，沉积速率从100厘米/千年大幅攀升至300厘米/千年，Fe/Ca比值与花粉通量均翻倍，共同指示陆源沉积物输入量升高。粒度测量与端元模拟结果表明，沉积物的河流搬运作用增强。公元650年起，菊苣亚科（Cichorioideae）植物的花粉占比从10%骤升至20%；蒿属（Artemisia，原文作Atemisia）与车前属（Plantago）的花粉含量亦自此开始上升。落叶栎属花粉占比呈下降趋势，而常绿栎属花粉占比几乎无变化。公元650年至850年陆源/河流输入量的陡然增加，在年代误差范围内与公元700年左右伊斯兰教传入摩洛哥（伊斯兰化）的时间相契合。历史证据表明，伊斯兰化进程推动了摩洛哥南部的人口增长与社会发展，包括畜牧活动扩张、森林砍伐与农业发展。牲畜活动压力可能改变了当地植被结构，这也解释了菊苣亚科、车前属与蒿属（这类包含大量杂草物种的类群）的花粉占比上升现象。其中山羊可能作为土壤侵蚀的主要驱动因素发挥了主导作用；过度啃食可能导致落叶栎属种群衰退，而常绿栎属在被啃食后萌生力更强，因此更易存活。公元850年至今，沉积速率、Fe/Ca比值与河流径流量均保持稳定，但花粉分析结果显示植被仍在持续退化。过去150年的花粉分析结果表明，当地橄榄与本土阿甘树的种植规模有所扩大，同时引入了澳大利亚桉树。摩洛哥南部人口的快速增长持续带来了扩大畜牧与农业活动的压力。[…]